If my PHD guiding graphs appear quite good but I am still getting slightly elongated stars and the images I am getting are gradually shifting in one direction in the field of view is this likely flexure?
Can a helical focuser with "slop" in a short focus refractor used as a guidescope contribute greatly to flexure or is it most likely the attachment rings?
Thanks in advance for any advice anyone can offer!
Hi John. if this is with your JMI, could also be the mirror shifting around slightly with attitude (eg settling on the supports or sliding sideways a tiny bit). If that is the case, OAG should fix it.
What direction is the elongation in? If it's along the RA axis, then it could be related to guide settings or problems with the mount tracking (spiky periodic error curve).
Craig Stark recommends glue - guess that would turn the superfinder into a dedicated guider - if araldite solves the problem though, its probably a cost effective solution.
I think that the main issue is the screw that sits inside the helical focuser is smaller in diameter than the worm channel thread in which it rotates. As well, there is a small gap in between the focuser and the sliding 1/ 1/4 barrel tube.
Is this meant to be good enough for a $400 80mm short focus refractor/finder? Can it be repaired or an alternative focuser sourced for an 80mm ID barrel?
Does look a bit sloppy John.
Is it more tight/less sloppy when fully turned in, even if the image is out of focus? If so, you could then focus by sliding the guide camera in and out manually and securing with the set screw?
Gary
Saw that vid, I would not guide with that unit as is. That sucker will move more than a schmidt-cassegrain mirror at different parts of the sky! Shame that you would even need to consider changing the focuser on a guide scope! I really hope that Lumicon can recommend a fix here... keep us posted.
1 Focus it then drill three holes x120 degrees through the thread and the focuser tube. Tap in some screws to fit and it won't move.or
2 Cling wrap over the thread then insert and wind to position - that will take up a lot of slack.or
3 Oil or wax the female thread and dry out the male thread - apply a thin layer of resin to male then screw in til set -... then focus as normal.
4 Screw dried male and female threads in to focus and then drizzle in some glue. allow to set
Wait til you want to photo sculptor - oag won't help you there!!(well it may be ok, but away from the milky way, I had a dickens of a job to find a star to track on)
Wait til you want to photo sculptor - oag won't help you there!!(well it may be ok, but away from the milky way, I had a dickens of a job to find a star to track on)
No probs so far - with a Lodestar and a 12.5" in the OAG have had no issues so far sol lets see.